Table 2.

PRA relaxivities from nitroxide experiments. Cr = Cr(C₂O₄)₃^3-, Fe = Fe(CN)₆^3-, Ni = NiEDDA⁰ and Ru = Ru(NH₃)₆³⁺. ^* indicates NiEDDA⁰ values included diamagnetics in solution.

Experiment	PRA	χ1 [MHz/mM]	χ2 [MHz/mM]	$\frac{{\chi }_2}{{\chi }_1}$
tempone	Cr	1.9±.1	2.94±.05	1.5
tempone	Fe	0.72±.02	0.91±.03	1.3
	Ni	0.67±.02	0.95±.01	1.4
	Ru	0.92±.02	1.28±.02	1.4
IASL	Fe	1.62±.02	2.06±.03	1.3
	Ni	0.61±.01	0.77±.01	1.3
	Ru	0.81±.02	1.01±.05	1.2
IAPCPSL	Cr	1.36±.06	2.30±.04	1.7
	Fe	0.71±.01	0.86±.02	1.2
*	Ni	0.68±.01	0.89±.02	1.3
	Ru	1.14±.03	1.42±.05	1.2
ASL-cys-allyl	Fe	1.01±.07	1.58±.03	1.6
	Ni	0.58±.01	0.93±.01	1.6
	Ru	0.91±.01	1.36±.01	1.5
ASL-cys-methyl	Fe	1.04±.01	1.60±.03	1.5
	Ni	0.61±.01	0.91±.01	1.5
	Ru	0.90±.01	1.35±.02	1.5
deuterated tempone	Cr	1.76±.02	2.84±.01	1.6
	Fe	1.17±.04	1.34±.03	1.1
	Ni	0.65±.01	0.90±.01	1.4
	Ru	0.91±.04	1.17±.02	1.3
TEMPO choline + charge	Fe	4.7±.1	6.5±.1	1.4
	Ni	0.62±.01	1.02±.01	1.6
	Ru	0.54±.01	1.06±.01	2.0
carboxy TEMPO - charge	Fe	0.180±.005	0.22±.01	1.2
	Ni	0.60±.02	0.94±.02	1.6
	Ru	1.56±.06	2.17±.02	1.4
MSL-PEG bead column	Fe	1.4±.2	0.45±.02	0.32
	Ni	0.58±.01	0.42±.03	0.72
	Ru	0.528±.005	0.54±.01	1.0
ASL-S1 Myosin S1 labeled at Cys707	Cr	0.040±.002
	Fe	0.069±.001
*	Ni	0.044±.001
	Ru	0.052±.004